public uint Decode(double p0)
{
checked // check for int overflow
{
var rangeDiff = hi - lo;
uint mid = Convert.ToUInt32(lo + p0 * (rangeDiff));
uint decompressedBit;
if (previousBytes <= mid)
{
hi = mid;
decompressedBit = 0;
}
else
{
lo = mid + 1;
decompressedBit = 1;
}
while ((lo & msb) == (hi & msb))
{
lo = lo << 1; // shift one written bit
hi = (hi << 1) | 1; // shift one written bit and set LSB to 1
previousBytes = (previousBytes << 1) | _sourceFile.Read();
}
return(decompressedBit);
}
}
public ArithmeticDecoder(BitFile sourceFile)
{
_sourceFile = sourceFile;
for (int i = 0; i < 32; i++) // initialize with first 4 bytes
{
previousBytes = (previousBytes << 1) | sourceFile.Read();
}
}
private void Compress(BitFile sourceFile, BitFile targetFile)
{
EncodeHeader(targetFile, sourceFile.Length);
var predictor = new Predictor();
var encoder = new ArithmeticEncoder(targetFile);
while (!sourceFile.IsEof)
{
var bit = sourceFile.Read();
double p0 = predictor.Predict();
// todo: remove casting
encoder.Encode((int)bit, p0);
predictor.Update((int)bit);
}
encoder.EncodeRemainingBits();
}
